The invention relates to a filter device having a housing, a stack of filter plates arranged therein at a distance to one another, an inlet for the fluid to be filtered, an outlet for the filtrate, which is connected to the inside of the filter plates in a conducting manner, and a cavity extending through the stack and formed by recesses in the filter plates.
Known filter devices of the previously mentioned type, consist typically of stacks of hollow filter plates, which are arranged in an essentially cylindrical and closed filter housing, as the case may be, also in a rotating manner. The fluid to be filtered is introduced into the housing by a pump, goes through the filter formed in the region of the surface of the filter plates, into the inside of the plates, where the filtrate is removed via a central channel. Such filter plates are known, for example, from German published patent application DE 196 24 176 A1 or European patent application publication EP 0 723 799 A1, and corresponding filter devices are known from German published patent application DE 196 24 176 A1, as well as from U.S. Pat. No. 5,326,512.
A problem with such filter devices is always the removal of the filter cake, which forms on the surfaces of the filter plates in the course of time. These residues must be removed where possible in a continuous manner, so that such a solid covering may not be able to form in the first place. The use of mechanical scrapers requires some effort with regard to design, and is typically only used with bio-filters, in order to keep the growth of the filter surface constant. Mechanical filter devices of the type being discussed here, are therefore mostly cleaned by back-flushing, which however disturbs the continuous operation of the plant, and furthermore reduces the usable quantity of the obtained filtrate.
It is already known from DE 196 24 176 to profile the filter plate on its surface, such that a certain radial pumping effect is produced on rotation of the filter plate stack, which is to ensure a flow on the filter surface, in particular for the removal of residues on the filter surface. The disadvantage with this known arrangement, however, is the fact that the pump effect, which arises on account of the surface profiling, is comparatively low, and thus the desired effect is not achieved or only to a very small extent. A quicker rotation of the plate stack, furthermore, leads to an increased mechanical loading of the whole filter device, and requires a higher energy input.
Against this background, it is an object of the invention to design a filter device of the known type, such that one may achieve a high filter and self-cleaning effect of the filter, with a design effort as simple as possible.